Określenie wydajności zastosowanego Schematu Wykopu Maszyną Drążącą

Deployment of a tunnel boring machine (TBM) for excavation of tunnel structures in particular rock mass environment requires to provide an efficient TBM advance rate by application of the proper excavation regime. The applied regime has to respond to the changes in the excavated rock mass and to the wear of cutting discs installed on the TBM cutterhead. The paper describes a method for the control of excavation efficiency using the excavation process variables monitored during the TBM operation, with subsequent calculation of specific cutting energy, contact pressure of cutting discs and theoretical torque of the TBM cutterhead.Rozmieszczenie Maszyny Drążącej (ang. TBM) do wykopu tuneli, w szczególności w przypadku masy skalnej, wymaga uzyskania wydajnego wykorzystania TBM poprzez zastosowanie odpowiedniego schematu wykopu. Użyty schemat powinien reagować na zmiany w masie skalnej i na zużycie tarczy tnących umieszczonych na głowicy skrawającej TBM. Artykuł opisuje sposoby kontrolowania wydajności wykopu poprzez sprawdzenie zmiennych wykopu obserwowanych podczas pracy TBM z późniejszymi wyliczeniami rozporządzalnej energii tnącej, nacisku tarcz tnących i teoretycznej wartości obrotu głowicy skrawającej TBM

Effects of Outer Membrane Protein TolC on the Transport of <i>Escherichia coli</i> within Saturated Quartz Sands

The outer membrane protein (OMP) TolC is the cell surface component of several drug efflux pumps that are responsible for bacterial resistance against a variety of antibiotics. In this research, we investigated the effects of OMP TolC on <i>E. coli</i> transport within saturated sands through column experiments using a wild-type <i>E. coli</i> K12 strain (with OMP TolC), as well as the corresponding transposon mutant (<i>tolC::kan</i>) and the markerless deletion mutant (Δ<i>tolC</i>). Our results showed OMP TolC could significantly enhance the transport of <i>E. coli</i> when the ionic strength was 20 mM NaCl or higher. The deposition rate coefficients for the wild-type <i>E. coli</i> strain (with OMP TolC) was usually >50% lower than those of the <i>tolC</i>-negative mutants. The measurements of contact angles using three probe liquids suggested that TolC altered the surface tension components of <i>E. coli</i> cells and lead to lower Hamaker constants for the cell–water–sand system. The interaction energy calculations using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory suggested that the deposition of the <i>E. coli</i> cell primarily occurred at the secondary energy minimum. The depth of the secondary energy minimum increased with ionic strength, and was greater for the TolC-deletion strains under high ionic strength conditions. Overall, the transport behavior of three <i>E. coli</i> strains within saturated sands could be explained by the XDLVO calculations. Results from this research suggested that antibiotic resistant bacteria expressing OMP TolC could spread more widely within sandy aquifers